Adding a hub with SignalR and Umbraco

Umbraco ships with signalR installed, find out how to add your own hub(s) to the existing setup

Umbraco ships with signalR installed. This article shows how to add your own hub(s) to the existing setup.

Create a hub and its interface

We are going to go for the most basic implementation possible, a status ping. So first create a new interface with the following code:

public interface ITestHubEvents
{
    // Define the events the clients can listen to
    public Task Pong();
}

And then the actual hub:

using Microsoft.AspNetCore.SignalR;

public class TestHub : Hub<ITestHubEvents>
{
    // when a client sends us a ping
    public async Task Ping()
    {
        // we trigger the pong event on all clients
        await Clients.All.Pong();
    }
}

Define a custom route

Next up, is defining a custom route. Use IAreaRoutes and the base Umbraco backend path so there's no need to reserve another path in the settings.

using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
using Umbraco.Cms.Core.Composing;
using Umbraco.Cms.Core.DependencyInjection;
using Umbraco.Cms.Web.Common.ApplicationBuilder;
using Umbraco.Extensions;

public class TestHubRoutes : IAreaRoutes
{
    private readonly IRuntimeState _runtimeState;
    private readonly string _umbracoPathSegment;

    public TestHubRoutes(
        IOptions<GlobalSettings> globalSettings,
        IHostingEnvironment hostingEnvironment,
        IRuntimeState runtimeState)
    {
        _runtimeState = runtimeState;
        _umbracoPathSegment = globalSettings.Value.GetUmbracoMvcArea(hostingEnvironment);
    }

    public void CreateRoutes(IEndpointRouteBuilder endpoints)
    {
        switch (_runtimeState.Level)
        {
            case Umbraco.Cms.Core.RuntimeLevel.Run:
                endpoints.MapHub<TestHub>(GetTestHubRoute());
                break;
        }

    }

    public string GetTestHubRoute()
    {
        return $"/{_umbracoPathSegment}/{nameof(TestHub)}";
    }
}

Add the routing to the Umbraco Composer

Last step in the setup is registering our custom route:

using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
using Umbraco.Cms.Core.Composing;
using Umbraco.Cms.Core.DependencyInjection;
using Umbraco.Cms.Web.Common.ApplicationBuilder;
using Umbraco.Extensions;

public class TestHubComposer : IComposer
{
    public void Compose(IUmbracoBuilder builder)
    {
        // first we are going to add signalR to the serviceCollection if no hubs have been added yet
        // this is just in case Umbraco ever decides to use a different technology
        if (!builder.Services.Any(x => x.ServiceType == typeof(IHubContext<>)))
        {
            builder.Services.AddSignalR();
        }
        
        // next is adding the routes we defined earlier
        builder.Services.AddUnique<TestHubRoutes>();
        builder.Services.Configure<UmbracoPipelineOptions>(options =>
        {
            options.AddFilter(new UmbracoPipelineFilter(
                "test",
                 endpoints: applicationBuilder =>
                {
                    applicationBuilder.UseEndpoints(e =>
                    {
                        var hubRoutes = applicationBuilder.ApplicationServices.GetRequiredService<TestHubRoutes>();
                        hubRoutes.CreateRoutes(e);
                    });
                }
            ));
        });
    }
}

Add the route in appsettings.json file

When setting up SignalR routes, add the route to ReservedPaths in the appsettings.json file like:

"Umbraco": {
    "CMS": {
        "Global": {
            "ReservedPaths": "~/app_plugins/,~/install/,~/mini-profiler-resources/,~/umbraco/,~/umbraco/testhub/,"
        }
    }
}

You need to provide the default reserved paths, else you'll run into an issue as mentioned on GitHub.

Test the setup

And lastly we can test the setup with some JavaScript in our view:

<!-- We reference the signalR js file that comes with Umbraco -->
<script type="text/javascript" src="/umbraco/lib/signalr/signalr.min.js"></script>
<script>
    var connection = new signalR.HubConnectionBuilder()
        .withUrl("/umbraco/testhub") // this is the url that we created in the routing `TestHubRoutes.GetTestHubRoute()`
        .withAutomaticReconnect()
        .configureLogging(signalR.LogLevel.Warning)
        .build();
    
    // register our callbacks when the hub sends us an event
        connection.on("Pong", function () {
            console.log("Pong");
        });

    // start the connection
    connection.start().then(function () {
        console.info("signalR connection established");

        // connection is established => call a function on the hub
        connection.invoke("Ping").catch(function (err) {
            return console.error("Could not invoke method [Ping] on signalR connection", err.toString());
        });
    }).catch(function (err) {
        return console.error("could not establish a signalR connection", err.toString());
    });
</script>

When you insert this in a view, you should see a signalR connection established console message followed by Pong.